Liquid level and temperature responsive control valve for refrigeration apparatus



Oct. 20, 1959 J N LONG 2,909,042

LIQUID LEVEL AND TEMPERATURE RESPONSIVE CONTROL VALVE FOR REFRIGERATION APPARATUS Filed Feb. 24, 1958 F I G I 6 EVAPORATOR J' ,2 CONDENSER 4 g I z I /8 t INVENT OR.

JOSEPH N. Lomq BY E z 7 2,909,042 Patented Oct. 20, 1959 LIQUID LEVEL AND TEMPERATURE RESPONSIVE CONTROL VALVE FOR REFRIGERATION AP- PARATUS Joseph N. Long, Wauwatosa, Wis., assignor to The Vilter Manufacturing Company, Milwaukee, Wis., a corporation of Wisconsin Application February 24, 1958, Serial No. 716,955 6 Claims. (Cl. 62-192) This invention relates to float control valves which are also sensitive to the temperature of the fluid with which they are in contact. The invention finds particular utility in refrigeration equipment and more particularly as an oil return control for the oil separator.

In refrigeration systems, a small amount of oil is carried through the compressor along with the refrigerant, in spite of efforts made to prevent it. This oil must be separated from the refrigerant before the latter is sent through the system and oil separators are provided for this purpose.

The heat of compression developed in the compressor is transferred to the oil separator and acts to evaporate the refrigerant that has condensed therein during a shutdown period. The oil that is returned to the compressor from the separator should be free of any liquid refrig erant and therefore the refrigerant should be completely evaporated before the oil separator control valve opens to permit return of oil to the compressor. In order for the refrigerant to be completely evaporated, the oil must first reach a predetermined temperature.

In accordance with the present invention, a control has been provided for an oil separator of a refrigeration unit, which control is sensitive to the liquid level of the oil in the separator and is also responsive to the temperature of the oil. The control assembly provided is particularly simple in construction and efficient in operation, being compact and easy to install or remove for maintenance purposes.

The invention provides a liquid level and temperature responsive control valve for a refrigeration system oil separator which insures that the oil returned to the compressor is completely free of any liquid refrigerant.

These and other objects and advantages of the invention will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings in which:

Figure 1 is a schematic diagram of a refrigeration system which would utilize the invention;

Figure 2 is a longitudinal cross-sectional view, on an enlarged scale, illustrating a control valve made in accordance with the present invention; and

Figure 3 is a transverse sectional view taken on lines 33 of Figure 2.

Referring more particularly to the drawings, the refrigeration system includes a liquid receiver which furnishes liquid refrigerant, such as ammonia, via conduit 11 to the evaporator 12.

The liquid picks up heat in the evaporator and the vaporized refrigerant is then pulled into the compressor 14 through the suction line 15.

The compressor delivers a mixture of oil and vaporized refrigerant into the oil separator 16 via the conduit 17 where its velocity is diminished and where the oil is separated from the refrigerant. The vaporized refrigerant is then conducted through the conduit 18 and into the condenser 19. The liquid refrigerant is then drained by gravity through conduit 20 and back to the liquid receiver.

Before returning oil back to the compressor via conduit 22, it is important that the oil be completely free of any liquid refrigerant which may be in the oil separator tank 16. The control valve 24 provided by this invention has proved completely successful in preventing refrigerant from returning to the compressor with the oil.

Two reasons, among others, which cause liquid refrigerant to form in the oil separator are, (1) if the refrigerant is highly saturated when it comes to the compressor, then under severe conditions of operation this liquid refrigerant will go through the compressor and into the separator and (2) if the compressor is shut down, the refrigerant may condense in the oil separator because the latter may be, and often is, the coldest location in the system.

Various attempts have been made heretofore to prevent the return of liquid refrigerant with the oil to the compressor including the provision of having a thermo bulb in the separator which was electrically connected to a solenoid, the solenoid in turn would then open a valve only when a predetermined temperature was sensed by the thermo bulb. However, such an arrangement is not only costly but it is also complex and creates maintenance and servicing problems. Bimetallic elements have also been proposed for changing the action of a float valve in other types of apparatus. The arrangement provided by the present invention is particularly simple but at the same time efiicient in performing the functions for which it was designed and in definitely holding the valve shut until proper temperature of the oil is reached and regardless of the position of its float.

As more clearly illustrated in Figures 2 and 3, the valve assembly includes a flanged head 26 which is securable to the oil separator and a valve support 27 which is threaded into the head and extends into the separator. The valve yoke support 28 is rigidly secured to the valve support and extends downwardly therefrom. A valve yoke or arm 29 is pivotally secured to the valve yoke support and carries a movable valve element in the form of a needle valve stem 32 on its horizontally disposed end. The support has a bore 33 extending longitudinally therein which communicates with a cross bore 34. A valve seat 35 is threadably engaged in bore 34 and the stem 32 is adapted to seat therein.

A float 36 is connected by the rod 37 to the other end of the yoke and as the level of the float in the separator lifts the float, the valve stem 32 will be withdrawn from its seat. A spring 39 tends to urge the float in a downward direction and serves to balance the weight of the float.

Thus the valve is regulated by the liquid level in the separator.

Means have also been provided to prevent the valve from opening and thereby permitting oil to return to the compressor, regardless of the position of the float mechanism, which means is controlled by the temperature of the oil. In other words, if the temperature of the oil is insutficient to completely evaporate the refrigerant, the valve will remain closed. As a result, the oil will be completely free of refrigerant when it is returned to the compressor.

A bi-metallic element 41 of generally U-shaped configuration is securely attached at one of its ends to the upper side of the support 27 by screws 42. The other end of element 41 extends under the stem-carrying end of yoke 29 and engages it to maintain the valve stern 32 seated until the oil reaches a predetermined temperature.

For example, at oil temperatures below approximately degrees F., the bimetal element holds the valve in the closed position. Upon starting the compressor, heat is added to the separator which evaporates any liquid refrigerant therein. When the oil temperatures rise above 100 degrees F., the refrigerant, such as ammonia, would be completely evaporated and the element would open to the dotted line position-allowing normal return of refrigerant-free oil to the compressor.

The particular arrangement shown of a bimetallic element for delaying the operation of a float valve has particularly good functional characteristics. By mounting theelement at the stem carrying end of the yoke 29, a smaller distance of element travel is required than if it were mounted on the top of the support and acted against the top end of the yoke and made to contract when heated. Disc shaped elements fastened directly to the needle stern have also been proposed but have proved to be unsatisfactory because they resulted in rather complicated structures.

The device made in accordance with the present invention is simple in construction which not only results in an economical structure to produce, but presents a minimum of service and maintenance problems. A small amount of element travel is sufficient to permit the return valve to be opened and thus insures only a working range over which the spring element will function properly. At the same time the element acts to hold the valve shut, regardless of float position, until a millciendy high oil temperature is reached, thereby insuring complete vaporization of the refrigerant.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In a refrigeration system having an oil separator and a compressor for delivering a mixture of oil and refrigerant thereto, a valve assembly securable in said separator and in communication with said compressor for admitting oil thereto; said assembly having a support, a pivotal member mounted on said support, a valve in said support including a movable element, said element being secured to said pivotal member for swinging therewith between valve open and closed positions, a float mechanism also secured to said member for urging the latter to an open position when the oil level in said separator rises beyond a predetermined height, and a temperature responsive U-shaped bimetal element fixed at one end to said support and having its other end engageable with said pivotal member for preventing movement of the latter until the separator oil reaches a predetermined temperature.

2. In a refrigeration system having an oil separator and a compressor for delivering a mixture of oil and refrigerant thereto, a valve assembly securable in said separator and in communication with said separator for returning oil thereto; said assembly having a support, an arm pivotally mounted on said support, a valve seat in said support, a movable valve element secured to said arm and shiftable between valve seat engaging and open positions, a float mechanism also secured to said arm for moving the latter to said open position when the oil level in said separator rises beyond a predetermined height, and a temperature responsive U-shaped bimetal element fixed at one end to said support and having its other end extending underneath and engageable with said arm for preventing movement of the latter in a valve opening direction until the separator oil reaches a predetermined temperature.

3. In a refrigeration system having an oil separator and a compressor for delivering a mixture of oil and refrigerant thereto, a valve assembly securable in said separator and in communication with said compressor for returning oil thereto; said assembly including a head having means for detachable securement to said separator, a support secured to said head and having a fluid passageway therein, a pivotal member mounted on said support, a valve seat in said support, a movable valve element, said element being secured to said pivotal member, a float mechanism also secured to said member for moving the latter to an open position when the oil level in said separator rises beyond a predetermined height, and a temperature responsive U-shaped bimetal element fixed at one end to said support and having its other end engageable with said pivotal member for preventing movement of the latter until the separator oil reaches a predetermined temperature, said assembly being detachable from said separator as a unit.

4. In a refrigeration system having an oil separator and a compressor for delivering a mixture of oil and refrigerant thereto, a conduit between said separator and said compressor for returning oil to said compressor, a valve assembly securable in said separator and in communication with said conduit for admitting oil thereto; said assembly including a support having a fluid passageway therein, a pivotal member mounted intermediate its length on said support, a valve seat in said support passageway, a movable valve element secured adjacent one end of said pivotal member for swinging between valve open and closed positions, a float mechanism secured adjacent the other end of said member for urging the latter to a valve open position when the oil level in said separator rises beyond a predetermined height, and a temperature responsive U-shaped bimetal element fixed at one end to said support and extending downwardly and beneath said member and having its other end engageable with said one end of pivotal member for preventing movement of the latter until the separator oil reaches a predetermined temperature.

5. A control device of the character described including a head adapted to be secured to a liquid tank in which the temperature is variable, a support secured to said head and adapted to extend into said tank, a valve seat in said support through which liquid may pass from said tank, an arm pivotally mounted on said support, a valve element secured to said arm adjacent one end thereof for swinging between positions in which it engages or opens said valve seat, float means secured to the other end of said arm for urging said valve element to said open position when said means is raised a predetermined amount, and a temperature responsive U-shaped bimetal element secured at one end to said support and having the opposite end thereof engaging said arm immediately adjacent said valve element for preventing valve opening movement thereof until said element reaches a predetermined temperature.

6. A liquid level and temperature responsive control device for a refrigeration system, said device including a head adapted to be secured to a liquid tank, a support secured to said head and adapted to extend into said tank, said support having a fluid passageway therein, a valve seat in said passageway through which liquid may pass from said tank, an arm pivotally mounted intermediate its length on said support, a valve element secured adjacent one end of said arm for swinging between valve seat open and closed positions, float means secured adjacent the other end of said arm for urging said valve element to open said position when said float means is raised a predetermined amount, and a temperature responsive U-shaped bimetal element fixedly secured at one end to said support and extending downwardly beneath with its opposite end engaging said one end of said arm immediately below said valve element for preventing valve opening movement thereof until said element reaches a predetermined temperature.

References Cited in the file of this patent UNITED STATES PATENTS 1,712,460 Purdy May 7, 1929 (Other references on following page) UNITED STATES PATENTS 2,338,319 Andrews Oct. 27, 1931 2,431,721 Williams Jan. 19, 1932 2,566,216 Terry Jan. 19, 1931 $634,746 Johnson Aug. 25, 1942 25704105 Hayter Dec. 14, 1943 6 De Laney Jan. 4, 1944 Wisman et a1. Dec. 2, 1947 Landon Aug. 28, 1951 Newton Apr. 14, 1953 Riemann et a1 Feb. 23, 1954 

